Cowling for air-cooled internal combustion engines



July 28, 1931. J. D. NORTH 1,816,544

COWLING FOR AIR COOLED INTERNAL COMBUSTION ENGINES Filed Jan. 21, 1931 CfSheets-Sheet 1 Fla. 1. FI

July 28, 1931. J. D. NORTH 1,816,544

COWLING FOR AIR COOLED INTERNAL COMBUSTION ENGINES Filed Jan. 21, 1931 3 Sheets-Sheet 2 July 28, 1931. J. D. NORTH ,8 6,

COWLING FOR AIR COOLED INTERNAL COMBUSTION ENGINES Filed Jan. 21, 1931 -3 Sheets-Sheet .3

Patented July 28, 1931v 1 1,816,544

; UNITED-STATES PATENT oFFm JOHN DUDLEY NORTH, OF NORWICH, ENGLAND, ASSIGNOR TO BOULTON & PAUL LIMITED, OF NORWICH, ENGLAND .COWLING FOR AIR-COOLED INTERNAL COMBUSTION ENGINES Application filed, January 21, 1931, Serial No. 510,313, and in Great Britain April 10, 1930.

This invention relates to cowlings for aireither at the leadingedge of the annular cooled engines of the type in which the cowlouter part so as to form a bulbous leading ing, in the form of a ring, is mounted around portion with the outwardly extending anor in front of the engine. In air-cooled ennular part at its after end or the annular 5 gines most efiicient cooling of the engine is 'deinner portion may be located at the trailing 55 sired by reason of the air flowing round the edge of the annular outer portion with the engine and minimum resistance, is also deoutwardly extending annular part at its forsired both in respect of the engine and of the Ward end. Further, two annular inner porcowling itself. tions may be provided, one at the leading It is already known that the air resistance edge of the annular outer portion and the so of an engine of the air-cooled radial type, other-at the trailing edge of the annular outer when mounted in front of the body of an aeroportion with the outwardly extending parts plane or other aircraft, may be considerably opposed to each other and spaced apart.

reduced by mounting in front of the engine a The length of the chord of the cowling cowling in the form of a ring which permits from the forward edge to the after edge may 65 of the entrance of the air necessary for cool be such as to enclose completely the engine ing the engine through a central orifice of the) within the cowling, or it may screen the en ring, which is appreciably smaller in diam gine in-advance of the cylinders and termieter than the diameter of the engine. The ail mate in a rearward direction around the cylinentering the ring after flowing past the engine ders, in the case of an engine of the radial 70 cylinders, emerges from the after border of type.

the ring where the interior diameter is ap- The invention will now be described with proximately that of the outer contour of the reference to the accompanying drawings ile g lustrating practical embodiments thereof, 1n

Cowling rings of this type have been sugwhich 75 gested, in which the material forming. such Figs. 1 toe}, illustrate diagrammatically the ring is of uniform thickness, and it has also method of forming the cowling accordlng to been proposed to make the ring of hollow one practical embodiment of this invention. form so that it may serve as a manifold for Fig. '5 illustrates the application of the the collection of exhaust gases from the encowling to a radial engine mounted on air- 80 gine. It is also known'that the resistance of craft, only one of the cylinders of the engine the engine body combined with the fuselage being shown in the drawings. may be still further reduced by the complete Fig. 6 is a front v1ew of the cowlmg shown enclosing of the engine in a cowl in which the in Fig. 5, removed from the engine.

I after end of the cowl extends behind the en- Fig. 7 is a sectional view on line 7-7 in 85 gine to a considerable extent. Fig. 6 and looking in the direction ofthe ar- According to this invention, we provide a rows. cowling for air cooled internal combustion Fig. 8 1s a sectlonalview on thehne 8-8 engines which is formed with an annular in Fig. (Sand looking in thedirectlon 0f the 40 outer portion /shaped to provide a streamline arrows. 90 flow for air over its outer surface and with an F igs. 9 and 1-0 are cross-sectional diagrams annular inner portion shaped to provide a of modlfied forms of the cowhng.

streamline flow for air over its inner surface, Fig. 11" 1s a cross-sectional diagram of a said annular inner portion terminating interfurther modified form of the cowling.

mediate the ends of the said annular outer Fig. 12is a similar View to Fig. 5, il- 95 portion in an annular part which extends outlustrating the application of the cowling acwardly at an angle to the annular inner part cording to F 1g. ll to an aircraft engine. and connects to the inner surface of the an- As illustrated 1n F1gs. 1 to 4, the shape or nular outer part. form of the bulbous portion 1s determinedby The annular inner portion may be located designing in the first instance a streamlme mining the form of the bulbous section is analogous to an already known method for determining the form of aircraft wing sections, and any of the known methods of computing the basic streamline shape as already known are used in the case of aircraft wing sections, may be employed for this purpose. It is the essence of these methods of computing shapes that give rise to a smooth and undisturbed airflow past them, that the rate of change of curvature of the surfaces past which the fair flows should itself be subj ect to no abrupt variations, and any suitable method ofensuring that the contours comply with this requirement may be employed in laying out the form of such a bulbous section.

The cowling is constructed, as shown in Fig. 3, of a sheet of metal a of annular form I bent to provide'a smooth curve in cross section such as would, for example, be used on the upper surface of an aircraft wing permitting smooth or streamline flow of air over the outer surface. This sheet of metal 0 extends from the point a representing the forward edge to the point a representing the after edge and the length of the chord of this Cowling from a to a is such that when the cowling is applied to an engine this engine is completely enclosed 'within the cowling, as shown in Fig. 5. Tothis oumr member a .is applied a leading portion which forms with the outer member a bulbous shape corresponding to that shown in Fig. 2. This leading portion of the bulbous shapeis formed by providing a sheet metal inner portion 6 which trails off to the outer portion a.

7 As shown in Fig. 4, however, this, inner portion trails ofi to a point marked 72 at aboutone-fourth of the chord of the outer member at which it extends outwardly at an angle to the part b forming a rear. annular ring a at the bulbous portion which extends outwardly to the outer portion a to which it is attached.

This 'foreshortening of the bulbous portion of the cowling. results in a departure of the inner surface of the cowling from the smooth curvature obtained w th the construction shown in Fig. 3. Prov ded that this departure acts at areasonab e distance back from the leading edge we have foundthat the departure may take the form of an abrupt step without detrimental effects.

' In its application to aircraft engines d with radial cylinder (1 this cowling is appliedasshwn in Fig. 5 with the bulbous portlon in front of the cylinders d; with the outer portion a extending over the ends of the cylinders, with the after end a behind the engine and with the cylinder heads d close to the internal surface of'the outer portion.- I

The bulbous portion may conveniently .be used as a collector and silencer for the exhaust gases from the engine d, the gases entering the ring through a series of pipes e, which pipes are fixed at one end to the exhaust ports of the cylinders d of the engine d and curved forwardly and outwardly and pass into the inner portion 6 of the bulbous portion adjacent the point 6 thereof. As

shown in Fig. 6 these exhaust pipes are lo-i cated at intervals around the interior of the cowling. The exhaust gases leave the bulbous "portionby means of two outlet pipes f, which pipes are fixed at their (forward end to the outwardly extending ring 0 and extend outwardly and rearwardly through holes a? in the outer portion" a. These outletpipes are located at the lower end of the oowling and are spaced apart one on either side thereof.

Shortly stated, the cowling constructed in accordance with this embodiment of the invention consists of a bulbous portion and an annular continuation of relatively thin-metal with a step between the bulbous portion and the continuation on the interior of the cowling.

Fig. 9 rangement in which the annular space is formed at the trailing portion. In this'case the cowling is constructed with the outer portion a in accordance with the previousplied an inner portion 9 extending forwardly from the trailing end a to a point 9 intermediate'the ends of the outer portion. The inner portion is constructed to a curved shape so as to provide for a smooth flow of air illustrates diagrammatically an arembodiment, and. to this outer portion is apover its surface. At the forward end of the inner portion is located an outwardly extending annular part h. which is constructed at an angle to the inner portion and is connected at its outer periphery to the inner surface of the outer annular portion a.. The

angle which the outwardly extending part subtends to the inner portion may be increased, -for instance, as indicated by the dotted lines in Fig. 9. In this arrangement the leading portion of the cowling will be of uniform thickness terminating at the leading edge a. I i

Fig. 10 is a similar view to Fig. 9 but formed with an outwardly extending partVz constructed of a curved shape.

Fig. 11 shows a further modification in i which the embodiments shown in Figs. 4 and 9 are combined. In this view partscorresponding to those in Figs. 4 and 9 are indicated by like reference numerals to those used in these figures. In this case, the annular inner portion 9 constitutes a continua- X tion of the streamline of the inner portion b of the bulbous leading portion. The cowling so made presents acomplete streamline section except for a portion midway between its leading and trailing edges. The outwardly extending annular part at the fore end of the annular space at the trailing edge as well as the outwardly extending annular part at the after end of the bulbous leading portion'may be curved inwardly or outwardly as I indicated by the dotted lines.

Fig..12 shows the application of the cowling constructed as shown in Fig. 11 to an aircraft engine With the exhaust ports facing to the rear. The exhaust ports of the engine are connected by the rearwardly and outwardly extending pipes, only one of which marked '13 is shown adapted to connect to the inner portion gat the after portion of the cowling. The annular space so formed at the trailing edge is thus used as a collector and silencer for the exhaust gases from the engine, gases entering this space through the pipes fixed to the exhaust ports and to the inner portion 9 and leaving the annular space at the trailing edge by means of outlet pipes j fixed at. their forward ends to the inner portion 9 and the outer portion a and extendlng rearwardly thereof.

\Vhat I claim as my invention and desire to secure by Letters Patent is 1. A cowling for air-cooled internal combustion engines formed with an annular outer portion shaped to provide a streamline flow for air over its upper surface, an annular inner portion shaped to provide a streamline flow for air over its inner surface, said annular inner portion terminating between the ends of said annular outer portion, and an outwardly extending annular part located at an angle to theannular inner portion and connected to the inner surface of the annular outer portion.

2. A cowling for air-cooled internal combustion engines formed with an annular outer portion shaped to provide. a streamline flow for air over its upper surface from a leading to a trailing edge, an annular inner portion located at the leading edge of the annular outer portion and shaped to provide a bulbous leading portion with a streamline flow for air over its inner surface. and an outwardly extending annular part at the after'en'd of said bulbous leading portion which outwardly extending annular part is set at an angle to the annular lnner portion and is connected to the inner surface of the annular outer portion.

3. A cowling for air-cooledinternal combustion engines formed with an annular. outer portion shaped to provide a streamline flow for air over its upper surface, an annular inner portion located at the trailing edge of the annular outer portion and shaped to provide a streamline flow for airover its inner sur-' face, and an outwardly extending annular part at the forward end of said annular inner portion which outwardly extending annular part is at an angle to the annular inner portion and is connected to the inner surface of the annular outer portion.

4. A cowling for air-cooled internal combustion engines formedwith an annular outer portion shaped to provide a streamline flow for air over its'upper surface from a leading edge to a trailing edge, an annular inner portion at the leading edge of said annular outer portion shaped to' provide a bulbous leading portion with a streamline flow for air over its inner surface, an outwardly extending annular part at the after end of said bulbous leading portion which outwardly extending annular part is set at an angle to the annular inner portion, an annular inner trailing portion located at the trailing edge of the annular outer portion and shaped to provide a streamline flow for air over its inner surface, and an outwardly extending annular part at the forward end of said annular inner trailing portion set at an angle to the annular inner trailing portion and connected to the inner surface of the annular outer portion.

5. A cowling for air-cooled internal; combustion engines formed with an annular outer portion shaped to provide a .streamline flow for air over its upper surface, from a leading edge to a trailing edge, an annular inner portion shaped to provide a streamline flow for extending annular portion set at an angle to the annular inner portion and connected to the inner surface ofthe annular outer portion, pipes for connecting said cowling to exhaustports on the internal combustion engine adapted to pass exhaust gases tosaid cowling, andan outlet pipe on said cowling adapted to allow said exhaust gases to leave said cowling. 6. .A cowlingfor air-cooled internal combustion engines formed with an annular outer portion shaped to provide a streamline flow for air over'its upper surface froma leading edge to a trailing edge, an annular inner portion located at the leading edge of the annular outer part and shaped to provide a hollow bulbous leading portion with a streamline flow for air over its inner surface, an outwardly extending annular part at the after end of sald bulbous leading portion which outwardly extending annular part is set at an angle to the annular inner portion-and is connected to the inner surface of the annular outer portion, pipes for connecting the hollow bulbous annular partadapted to allow the exhaust gases to leave said bulbous leading portion.

A 7. A cowling for air-cooled internal combustion engines formed with an annular outer portion shaped to provide astreamline flow for air over its upper surface, an annular inner portion located at the trailing edge of the annular outer portion and shaped to provide a hollow trailing portion with a streamline flow for air over its inner surface, an outwardly extending annular part at the forward end of said annular inner portion which outward- 1y extending annular part is set at an angle .to the annular inner portion and is connected to theinner surface of the annular outer por- 1 tion, pipes for connecting the hollow trailing portion to exhaust ports on the internal com= bustionengine adapted to pass exhaust gases I to said hollow trailing portion and outlet pipes adapted to allow said exhaust gases to leave the hollow trailing portion.

' 8. A cowling for air-cooledinternal combustion engines formed with an annular outer portion shaped to provide a streamline flow for air over its upper surface from a leading 5 edge to a trailing edge, an annular'inner portion shaped to provide a streamline flow for air over its inner surface, said annular inner. portion terminating between the edges of said outer portion, and an outwardly extending annular part curved in cross-section set at an angle to the annular inner portion and connected at'its outer periphery to the inner surface 0f the annular outer portion.

In witness whereof I have hereunto setmy hand. V

JOHN DUDLEY NORTH. 

